Soil often erodes from a construction site when rain falls on bare ground left exposed during construction work. Various methods, from staked hay bales to engineered silt fences, are used to control soil erosion. A silt fence is a temporary barrier designed to inhibit sediment from migrating away from construction sites via storm water runoff to protect water quality in nearby streams, rivers, lakes, and seas. The fence retains sediment primarily by retarding flow and promoting deposition on the uphill side of the fence. Runoff is also filtered as it passes through the material of the fence. Silt fences are widely used on construction sites in North America and elsewhere because of their low cost and simple design although their effectiveness in controlling sediment is often rather limited because of problems with design, installation, maintenance, or any combination of these.